Handsets used in the cellular communications industry benefit from optimum performance from antenna systems in order to maximize the two-way voice or data link between a remote base station and the handset. Most current cellphone antennas utilize either dipole, or half-dipole antennas, mounted external or internal to the handset, all of which may be susceptible to RF radio frequency loss to the hand and other inefficiencies related to their size and location on the handset.
For many modern environments, multiple signal bands are accessed by wireless communications devices. For example, a wireless communications device may access both the 824-960 MHz band and the 1710-2170 MHz band.
FIG. 19 depicts a prior art antenna system of a wireless communications device (WCD) 140 including a quarter wavelength conductor 142 which is fed at location 144 by a low impedance RF transmission line (not shown) against ground plane conductor 143. Ground plane conductor 143 may be formed by the ground traces of a printed circuit board (PCB) of a WCD, such as a cellular handset. A half-wavelength dipole antenna results with an extending portion of the antenna depicted with a length, L.
FIG. 20 illustrates another antenna system 140 of the prior art wherein the quarter wavelength whip conductor 145 is coiled to reduce its overall length.
FIG. 21 illustrates another antenna system 140 of the prior art wherein the quarter wave upper element is formed by a serpentine conductor 146 and fed at location 148 and junction 144. Location 148 is selected along conductor 146 to provide a good RF impedance match to a transmission line. Additional information may be found at U.S. Pat. No. 6,239,765, entitled Asymmetric Dipole Antenna Assembly, incorporated by reference herein.
FIGS. 22 and 23 illustrate a prior art WCD 170 which includes a planar inverted “F” antenna (PIFA) 180 shown schematically as mounted above ground plane conductor 183. Many PIFA designs have the PIFA end connected to the ground plane conductor 183 at location 187, which may be either of the two longitudinal ends of WCD 170. The PIFA antenna 180 overlays the ground plane conductor 183 and the PIFA free end (opposite location 187) is directed toward the opposite end 189 of the ground plane conductor 183.
A need remains for antenna systems providing wide VSWR voltage standing wave ratio bandwidth, high gain, and high efficiency. A need also remains for antenna systems providing such performance characteristics across multiple operating bands within a given environment.